The present invention relates to a transport peptide for delivering therapeutic and reporter proteins into cells, and vectors capable of expressing such proteins. More specifically it relates to the use of a bovine herpesvirus protein as part of a fusion protein that can be used for such purposes.
An important challenge facing the biomedical field is the need to provide effective methods to introduce therapeutic and reporter proteins into cells. While various existing approaches are adequate in some situations, they are usually deficient in others.
In G. Elliott et al., 73 J. Gen. Virol. 723-726 (1992); G. Elliott et al., 88 Cell 223-233 (1997); and A. Phelan et al., 16 Nat. Biotech. 440-443 (May 1998) the authors describe a human herpesvirus protein "HSV-VP22". They suggest that it may assist the delivery of proteins that are fused to it to surrounding cells. The disclosure of these publications and of all other publications referred to herein are incorporated by reference as if fully set forth herein.
However, there are safety concerns involved in using proteins from human herpesvirus in vivo in a human, and the efficiency of such a system appears to be undesirably low.
Moreover, the HSV-VP22 protein is a relatively large protein. Thus, due to its size, it is projected to be more likely to interfere with the activity of certain linked effectors, and/or may induce an antibody response.
In X. Liang et al., 69 J. Virol. 3863-3867 (1995) and X. Liang et al., 15 Vaccine 1057-1064 (1997) a bovine herpesvirus gene was described. In X. Liang et al., NCBI Entrez, (Accession U21137) (1996) the nucleotide sequence of this bovine gene (SEQ ID NO: 1) and its protein product (SEQ ID NO: 2) were provided. The gene was being studied in connection with vaccine research.
HSV VP22 is a 38 kD protein of 302 amino acids (906 bp of DNA) while the aforesaid bovine protein is a 32 kD protein of 259 amino acids (777 bp of DNA). Further, utilizing a computer program we determined that there was only about 28.7% amino acid identity between the two proteins.
A need therefore exists for an improved delivery system for delivering biotherapeutic proteins of interest to mammalian cells.